Fromageot et al., in Tetrahedron 23, 2315 (1967) describe the reaction of ribonucleosides, such as cytidine, with trimethylorthoacetate to yield the corresponding 2',3'-O-methoxyethylidene derivative and then hydrolyzing with aqueous acid under mild conditions to produce a mixture of 2'- and 3'-O-acetates in a yield of 74%.
Logue in Carbohydrate Research 40, C9-C11 (1975) discloses the reaction of 2',3'-O-(methoxyethylidene)-uridine with trimethylchlorosilane in acetonitrile under reflux for 10 minutes to produce 3'-O-acetyl-2,2'-anhydro-1.beta.-D-arabinofuranosyluracil hydrochloride in 72% yield.
U.S. Pat. No. 3,709,874 describes the preparation of 3'-O-acyl-2,2'-anhydro-1.beta.-D-arabinofuranosyl-5-fluorocytosines by selective hydrolysis of the corresponding 3',5'-O-diacyl derivatives.